Lubricating oils have been used in internal combustion engines, power transmission components, shock absorbers, power steering devices and the like. Crank case lubricants, i.e., oils for internal combustion engines, are formulated to perform a number of functions. The most important of these is to reduce friction on and wear of the engines pistons, valves, rings and the like. Engine oils also are formulated to protect metal surfaces against rust and corrosion, to provide oxidation stability, minimize deposits, and to flush out contaminants.
The performance of lubricant oils is a function of the additive composition they contain. The most common types of additives are: antiwear agents, extreme pressure (EP) agents, antifoams, antioxidants, detergents, dispersants, viscosity-index improvers, rust inhibitors, corrosion inhibitors, friction modifiers, and pour point depressants.
Unfortunately the effectiveness of any combination of additives cannot be predicted because of factors such as physical and chemical compatibility, for example. Also, while a given lube additive may contribute to the enhancement of one property of the lubricant composition often it has a negative impact on another property of the lubricant composition.
Among the many additives that are used in automotive engine lubricants are zinc compounds such as zinc dialkyldithiophosphate, molybdenum compounds such as molybdenum dithiocarbamate, calcium salts such as calcium sulfonate and borated compounds such as borated hydrocarbon-substituted succinic acid compounds. Because these additives produce ash deposits when used in internal combustion engines, they cannot be used in aviation piston engine lubricant compositions. Thus, one object of the present invention is to provide a lubricating composition for aviation piston engines that does not contain ash forming additives.
Another object of this invention is to provide a lubricating oil for aviation piston engines that has enhanced oxidative and thermal stability with sufficient solvency for fuel degradation products thereby reducing undesirable engine deposits.
Additional objects and advantages will be set forth in or will be obvious from the discussion of the invention.